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The Bilbao estuary (SE Bay of Biscay) is a recovering ecosystem whose sediments are still contaminated. They represent a potential risk for the biota including benthic and demersal species living in direct contact with the sediment. In this context, the present study aims to survey trends of the health status of the Bilbao estuary based on sediment chemistry and sole (Solea spp.) histopathology. Monitoring campaigns were carried out every autumn from 2011 to 2017 along the estuary. Contaminant levels were measured in sediments; liver, gills and gonads of juvenile fish were collected for histopathology. Overall, contaminant levels fluctuated throughout the years, with highest values recorded in the earlier years of the study period. Sole histopathology showed alterations of mild severity. Results permitted to assess the environmental health status of the Bilbao estuary during 7 years, although no clear temporal trend was detected. Longer-term monitoring programmes are necessary to confirm the ecosystem recovery., (Copyright © 2019. Published by Elsevier Ltd.)

The accidental spilling of petroleum oils into natural water resources expose fishes in the effluent area to serious problems.. Oreochromis niloticus were used in the current study as a model to investigate the toxicity of used engine oil and to evaluate the protective role of vitamin C against this toxicity. The oil concentration used in this study was previously determined to be 0.25 ml/l by 96 h-LC50. After 21 days of engine oil exposure, haematological and biochemical analyses revealed significant reduction in RBCs counts, haemoglobin concentrations and total proteins. However, ALT, AST and glucose levels were significantly increased by the end of the experiment indicating the damaging effects of the oil on fish tissues. Oxidative stress biomarkers were also measured; liver CAT activity was significantly decreased in the oil exposed group compared to control group, while MDA levels were significantly elevated. Histopathological examination showed the presence of several alterations in hepatic and branchial tissues in exposed group compared to the control group. Significant elevations in CYP1 A1 mRNA expression levels in hepatic tissue were also detected in the group exposed to used engine oil compared to the control group. However, supplementation of fishexposed to used engine oil with vitamin Csignificantly enhance the biochemical, oxidative and histological parameters., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

To evaluate the impact of DCAcAm on zebrafish gill, we measure the responses of antioxidant enzyme (superoxide dismutase, SOD), lipid peroxidation (malondialdehyde, MDA), ATPase (Na + /K + -ATPase and Ca 2+ /Mg 2+ -ATP) and histopathological changes of gill in adult zebrafish, after exposed to different concentrations of DCAcAm (0, 1, 10, 100, and 1000 μg L -1 ) for 30 days. Results indicated that DCAcAm first increased and then decreased SOD activity, and DCAcAm also lowered the activities of Na + /K + -ATPase and Ca 2+ /Mg 2+ -ATPase. These results indicated that high affinity of DCAcAm probably be a main factor, which can damage the structures of enzymes, thereby inhibiting the SOD and ATPase activities. Besides, histopathological investigation results also manifested that chronic exposure to DCAcAm can damage the gill tissues, disrupting the normal function of gills. We conclude that chronic exposure to DCAcAm was harmful to organisms, not only influence gill function, but also further cause damage on the gill tissues., (© 2019 Wiley Periodicals, Inc.)

Flowback and produced water (FPW) is a complex, often brackish, solution formed during the process of hydraulic fracturing. Despite recent findings on the short-term toxicity of FPW on aquatic biota, longer-term impacts of FPW on fish have not yet been investigated and the mechanisms of chronic effects remain unknown. The aim of the present study was to observe the effect of a diluted FPW on ionoregulatory endpoints in the rainbow trout Oncorhynchus mykiss, following a 28-d sub-chronic exposure. A salinity-matched control solution (SW), recreating the salt content of the FPW, was used to differentiate the specific effect of the salts from the effects of the other FPW components (i.e. organics and metals). Overall, fish ionoregulation was not impacted by the chronic exposure. An accumulation of strontium (Sr) and bromide (Br) occurred in the plasma of the FPW-exposed fish only, however no change of plasma ions (Na, K, Cl, Ca, Mg) was observed in SW- or FPW-exposed fish. Similarly, exposures did not alter branchial activity of the osmoregulatory enzymes sodium/potassium ATPase and proton ATPase. Finally, FPW exposure resulted in modifications of gill morphology over time, with fish exposed to the fluid displaying shorter lamellae and increased interlamellar-cell mass. However, these effects were not distinct from morphological changes that also occurred in the gills of control groups., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The present systematic experiment was conducted to estimate the impact of behavioral and pathological indices on freshwater fish Channa punctatus exposed to sub-lethal concentration (5 ppm) of an organophosphorus insecticide chlorpyrifos (CPF). Fish were segregated into four experimental groups (G1, control; G2, 10 days; G3, 20 days; and G4, 30 days exposure), each group comprises 15 fish in triplicate. The behavioral and histological changes were assessed in each group. Severe behavioral changes were observed in the 30 days, moderate changes in the 20 days, and mild changes in the 10 days exposure groups respectively when compared with the control group. The pathologic lesions such as inter lamellae space, necrotic lamellae, fused lamellae, and lifting of lamellae epithelium in gills; vacuolation, blood conjunctions, and necrotic hepatocytes in the liver; and lamina propria, fusion of villi, and flattened villi in the intestine were observed. These structural alterations of the gills, liver, and intestine could affect respiration, osmotic and ionic regulation; absorption, storage and secretion; digestion; and absorption of nutrients respectively, which in turn could adversely affect the growth and survival of freshwater fish Channa punctatus. This study serves as a biomonitoring tool for the effects of organophosphorus insecticide CPF on the aquatic biota.

Inappropriate processing and disposal of electronic waste contributes to the contamination of aquatic systems by various types of pollutants such as the rare-earth elements (REE) in which lanthanum (La) is included. Knowledge on the toxicity of these elements in marine organisms is still scarce when compared to other metals such as mercury (Hg) and arsenic (As). Therefore, this study aims to assess the toxicity of La on the mussel Mytilus galloprovincialis, considered a good bioindicator of aquatic pollution, through the analysis of metabolic, oxidative stress, neurotoxicity and histopathological markers. Organisms were exposed to different concentrations of La for a period of 28 days (0, 0.1, 1, 10 mg/L) under controlled temperature (18 °C ± 1.0) and salinity (30 ± 1) conditions. La concentrations in mussels increased in higher exposure concentrations. La exposure demonstrated a biochemical response in mussels, evidenced by lowered metabolism and accumulation of energy reserves, activation of the antioxidant defences SOD and GPx as well as the biotransformation enzymes GSTs, especially at intermediate concentrations. Despite oxidative stress being shown by a decrease in GSH/GSSG, oxidative damage was avoided as evidenced by lower LPO and PC levels. Inhibition of the enzyme AChE demonstrated the neurotoxicity of La in this species. Histopathological indices were significantly different from the control group, indicating impacts in gonads, gills and digestive glands of mussels due to La. These results show that La can be considered a risk for marine organisms and thus its discharge into the environment should be monitored., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Two aqueous fixation methods (modified Davidson's solution and modified Davidson's solution with 2% (w/v) Alcian blue) were compared against two non-aqueous fixation methods (methacarn solution and methacarn solution with 2% (w/v) Alcian blue) along with the standard buffered formalin fixation method to (a) improve preservation of the mucous coat on Atlantic salmon, Salmo salar L., gills and (b) to examine the interaction between the amoebae and mucus on the gill during an infection with amoebic gill disease. Aqueous fixatives demonstrated excellent cytological preservation but failed to deliver the preservation of the mucus when compared to the non-aqueous-based fixatives; qualitative and semi-quantitative analysis revealed a greater preservation of the gill mucus using the non-aqueous methacarn solution. A combination of this fixation method and an Alcian blue/Periodic acid-Schiff staining was tested in gills of Atlantic salmon infected with amoebic gill disease; lectin labelling was also used to confirm the mucus preservation in the methacarn-fixed tissue. Amoebae were observed closely associated with the mucus demonstrating that the techniques employed for preservation of the mucous coat can indeed avoid the loss of potential mucus-embedded parasites, thus providing a better understanding of the relationship between the mucus and parasite., (© 2019 John Wiley & Sons Ltd.)

In human-altered rivers, fish are often conjointly exposed to an increase in water temperature due to global warming and to a contamination by organic pollutants such as pesticides, but their combined effects are still elusive. Thermal and chemical stressors could potentially interact because high temperature increases metabolism and toxicant uptake, and can alter the ability of organisms to set up adequate stress responses and to maintain homeostasis. These combined stressors could thus potentially result in higher level of molecular and cellular damage, and stronger effects on behavior and physiology, but experimental evidence across biological levels is still scarce. In this study, goldfish Carassius auratus were experimentally exposed to an environmentally realistic cocktail of pesticides (S-metolachlor, isoproturon, linuron, atrazine-desethyl, aclonifen, pendimethalin and tebuconazol) commonly found in rivers of South-West of France at low or high dose in two different thermal conditions: a common summer temperature (22 °C) or a high temperature recorded during heat waves (32 °C). Results showed that high temperature alone caused behavioral and physiological changes (increased swimming activity, increased hepatosomatic index, decreased reproductive index) but limited cellular damage. However, high temperature aggravated the effects of pesticides at the molecular and cellular level. Indeed, pesticide exposure resulted in higher genotoxic effects (micronuclei rate) and irreversible cellular damage of the gills and liver (apoptosis, inflammation, necrosis) at 32 °C compared to 22 °C. This suggests potential synergistic effects of climate change and pollution, and highlights the need for multiple stress approaches to better predict the impacts of human activities on aquatic wildlife., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Microscopic plastic (MP) particles are a ubiquitous contaminant in aquatic environments, which may bind hydrophobic chemicals, such as polycyclic aromatic hydrocarbons (PAHs), altering their environmental fate and interactions with biota. Using rainbow trout gill (RTgill-W1) and intestinal (RTgutGC) epithelial cells we investigated the effects of polystyrene microbeads (PS-MBs; 220 nm) on the cyto- and genotoxicity of the environmental pollutants benzo[a]pyrene (BaP) and 3-nitrobenzanthrone (3-NBA) over 48 h (0, 0.1, 1 and 10 μM). The Alamar Blue bioassay, used to assess cytotoxicity, showed that both pollutants significantly decreased cell viability by 10-20% at 10 μM in both cell lines after 48 h whereas PS-MBs (5 or 50 μg mL -1 ) were non-toxic. Cytotoxicity in cells treated with PS-MBs together with BaP or 3-NBA were similar to those observed after exposure to BaP or 3-NBA alone. Using the formamidopyrimidine-DNA glycosylase (FPG)-modified comet assay 3-NBA, but not BaP, induced DNA damage in RTgutGC cells at 10 μM (∼10% tail DNA in the absence and ∼15% tail DNA in the presence of FPG versus ∼1% in controls), whereas PS-MBs alone showed no detrimental effects. Interestingly, comet formation was substantially increased (∼4-fold) when RTgutGC cells were exposed to PS-MBs (50 μg mL -1 ) and 10 μM 3-NBA compared to cells treated with 3-NBA alone. Further, using 32 P-postlabelling we observed strong DNA adduct formation in 3-NBA-exposed RTgutGC cells (∼900 adducts/10 8 nucleotides). 3-NBA-derived DNA adduct formation was significantly decreased (∼20%) when RTgutGC cells were exposed to MB and 3-NBA compared to cells treated with 3-NBA alone. Our results show that PS-MBs impact on the genotoxicity of 3-NBA, causing a significant increase in DNA damage as measured by the comet assay in the intestinal cell line, providing proof of principle that MPs may alter the genotoxic potential of PAHs in fish cells., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Iron is an essential element for many physiological functions of several organisms but in excess it causes toxicity. High iron content in water bodies of mountainous states is considered as one of the major factor, responsible for low productivity in aquaculture systems. But, till date comprehensive reports on the adverse effect of iron overload in aquatic organisms, especially cultured fishes are scanty. Therefore, the present study was undertaken to investigate the adverse effects of iron overload in economically important aquaculture fish species Labeo rohita. Three sub-lethal test concentration of iron (ferrous) viz., 1/16th, 1/8th and 1/4th of LC 50 (post 96 h) i.e. 8.25, 16.51 and 33.01 mg L -1 , respectively, were used for in vivo exposure. Blood cells and tissue samples of the control & exposed specimens were sampled at intervals of 24, 48, 72 and 96 h to assess alterations in hematological, oxidative stress and histological parameters. Significant changes in erythrocyte and leukocyte counts, hemoglobin, lipid peroxidation, antioxidant enzyme activity (super oxide dismutase and catalase) and tissue iron accumulation were observed in the exposed fish. Significant increase in lipid peroxidation, coupled with significant reduction in free radicals scavengers like super oxide dismutase and catalase revealed a compromised anti-oxidative defense mechanism in the fishes exposed to iron overload. Histological examination of gills and liver showed severe tissue injury and histological alternations. Severity was found to increase in time and concentration dependent manner. Perl's staining revealed accumulation of excess iron in liver of the exposed fish. The observed patho-physiological changes in the present study provide the most comprehensive insight of iron overload stress in L. rohita., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Metals, whether essential (Cu, Zn, Cr, Fe, Mn) or non-essential (Al, As, Cd, Ni, Pb, Hg) for organism metabolism, occur naturally in the marine environment and their abundance can increase due to the presence of human activities. In this study, fish were used as bio-indicators, to determine a correlation between the bio-accumulation of metals in muscle and gill tissues and the health status of fish. The study area was the Gulf of Tigullio (north-western Italy), which is impacted by various sources of metal contamination. Histopathology served as a significant tool to investigate possible alterations in gills, one of the main organs involved in fish physiology. Results highlighted some correlations between certain metals (e.g. Pb, Ni) and gill alterations (e.g. epithelial hyperplasia, epithelial lifting), providing baseline data from a pool of different fish species, which can be used for comparison purposes in further studies., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The present study delineate the various biochemical and histopathological tool to evaluate as strong biomarker in the field condition for detection of the least and maximize level of pollution and contamination. We have collected Labeo rohita from 13 different sites from East Kolkata wetland to determine biochemical and histopathological status to analyse metal contamination in the significant biological hot spot EKW. The biochemical marker as antioxidative status, i.e., catalase, superoxide dismutase (SOD), and glutathione-S-transferase (GST) in liver and gill, were remarkably higher (p < 0.01) at some of the sampling sites, but catalase in brain, SOD in kidney, GST in brain and kidney, and neurotransmitter as acetylcholine esterase (AChE) in brain were not significant (p > 0.05) among the sampling sites. The glycolytic enzymes, such as lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in liver, gill, and muscle, and protein metabolic enzymes, such as alanine amino transferase (ALT) and aspartate amino transferase (AST) in liver, gill, muscle, and kidney, were noticeably higher (p < 0.01) at some of the sampling sites. The histopathology of the liver and gill were altered at different sampling sites, such as blood congestion, leucocyte infiltration with parenchymal vacuolisation, nucleus with blood vessels, hepatocytes granular degeneration, haemorrhage, karyorrhexis, shrink nucleus, and pyknotic nuclei in liver. In the gill, structural changes, such as complete destruction and shortening of secondary gill lamellae, blood vessel in gill arch, curling of secondary gill lamellae, aneurism in gill lamellae, and neoplasia, were observed. Most of the metals were found within the safe limit all along the 13 sampling sites, indicating that fishes are safe for the consumption. Based on our finding, we could recommend that a rational application of biochemical profiles, such as oxidative and metabolic stress parameters, including histopathology to be used as biomarkers for biomonitoring the metal contamination in the aquatic environment.

The catfish, Clarias gariepinus, was exposed to different acute concentrations (5-10 mg/l) of diazinon and the Lc50 value was recorded as high as 7.3 mg/l for 96 hours. The fishes exposed to three sub-lethal levels of diazinon (0.73, 1.095 and 1.46 mg/l) for 30 days showed that the pesticide induces changes in different blood parameters. Number of red blood cells (RBC), haemoglobin level and haematocrit values were elevated whereas white blood cells (WBC) count was reduced. Various blood indices like mean corpuscular volume (MCV), mean corpuscular haemoglobine (MCH) and mean corpuscular haemoglobine concentration (MCHC) vary insignificantly in the fish treated with diazinon. Glucose level and activity level of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was increased in Clarias gariepinus exposed to diazinon. Protein level in plasma of fish treated with pesticide was changed but the change was insignificant. Histological changes in the liver, gills and kidney of fishes exposed to diazinon were apparent when compared to control. Hepatocytes necrosis and bleeding were more distinct in the fishes exposed to pesticide. Glomerulus hypertrophy and bleeding in kidneys; and fusion and degeneration of secondary lamellae and epithelial hyperplasia in gills were also observed in the exposed fish.

Pantanal shrimp Macrobrachium pantanalense was exposed for 96 h to the cypermethrin-based formulation Barrage ® . Population-relevant endpoints (survival, swimming behavior) as well as histopathology of gills were analyzed. A 96 h-LC 50 of 0.93 μg/L of cypermethrin was calculated while equilibrium disturbances were observed at 1.25 μg/L. Histological examination showed predominantly regressive changes in the gills of shrimp exposed to concentrations of 0.25 and 1.25 μg/L. Three levels of lesions were observed in the gills: I- Intercellular edema, epithelial lifting of the lamellae and lamellar fusion, fat vacuoles and hypertrophy of gill epithelial cells or mucous cells; II- nuclear changes, atrophy (reduction of volume and number) and hyperplasia of gill epithelia and III- necrosis. This study shows the high sensitivity of the shrimp M. pantanalense to the pesticide Barrage ® highlighting the importance of monitoring agrochemicals residues in the Pantanal region (Brazil) and conduct risk evaluation studies to prevent deleterious effects on the aquatic communities of Pantanal., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The effect of increasing ocean water temperature on morpho-functional traits of Antarctic marine species is under intense attention. In this work, we evaluated the effects of acute heat stress on the gills of the Antarctic haemoglobinless Chionodraco hamatus and the red blooded Trematomus bernacchii in terms of morphology, heat shock response, antioxidant defense and NOS/NO system. We showed in both species that the exposure to high temperature (4 °C) induced structural alterations, such as epithelial lifting and oedema of secondary lamellae. By immunolocalization we also observed that HSP-90, HSP-70, Xantine Oxidase, Heme Oxigenase and NOS are expressed in both species under control conditions. After heat stress the signals increase in C. hamatus being absent/or reduced in T. bernacchii. Our preliminary results suggest a specie-specific morpho-functional response of the gills of the two Antarctic teleosts to heat stress., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

As one of the mucosal lymphatic tissues, the gill is an important immune organ in fish. Water environmental pollutants enter fish body through the gill. Therefore, the gill is the initial site where pollutants produce toxic effects in water. Chlorpyrifos (CPF), a broad-spectrum organophosphate insecticide, is widely used for agricultural pests and causes river pollution. In the present study, we investigated histopathological effect, oxidative stress indexes (SOD, GSH, T-AOC, and MDA), and apoptosis-related genes (P53, PUMA, Bax, Bcl-2, Apaf-1, Caspase-9, and Caspase-3) in the gills of common carp exposed to CPF. The results indicated that CPF exposure decreased SOD, T-AOC, and GSH; increased MDA; decreased Bcl-2 mRNA expression; and increased P53, PUMA, Bax, Apaf-1, Caspase-9, and Caspase-3 mRNA expressions in common carp gills. Our results proved that CPF exposure caused oxidative stress and apoptosis in common carp gills; CPF exposure destroyed the structural integrity and affected the immune function through oxidative stress and apoptosis in common carp gills. These will provide evidence for the toxic effects of water environmental pollutants on immune function and structural integrity in fish gills., (Copyright © 2018. Published by Elsevier Ltd.)

The current study conducted to investigate the hypothesis that low or excess levels of lipids increased the gill rot morbidity through impairing the immune function and structural integrity in the gill of grass carp (Ctenopharyngodon idella). A total of 540 young grass carp with an average initial weight of 261.41 ± 0.53 g were fed diets containing six graded levels of lipids at 0.59%, 2.14%, 3.60%, 5.02%, 6.66% and 8.01% diets for 8 weeks. After the growth trial, fish were challenged with Flavobacterium columnare for 3 days. The results indicated that compared with optimal lipids supplementation (2.14%-8.01% lipids diets), low or excess levels of lipids impaired fish immune function through declining the activities of humoral compounds, down-regulated the mRNA levels of anti-inflammatory cytokines, inhibitor of κBα (IκBα) and ribosomal p70S6 kinase (S6K1), and up-regulated pro-inflammatory cytokines, nuclear factor κB p65 (NF-κB p65) (not p52), IκB kinase α (IKKα) (not IKKβ), IKKγ and eIF4E-binding protein (4EBP) in the gill of young grass carp. In addition, low or excess levels of lipids decreased young grass carp physical barrier function through down-regulating the mRNA levels of ZO-1 (rather than ZO-2b), Claudin b, c, 3, 12, 15a, 15b, 7b, 7a and Occludin through MAPKK 6/p38 MAPK/MLCK signaling molecules, decreasing antioxidant ability via Kelch-like ECH-associating protein 1a (Keap1a)/NF-E2-related factor 2 (Nrf2) signaling molecules, and down-regulating the mRNA levels of B-cell lymphoma-2 (Bcl-2) and inhibitor of apoptosis protein (IAP) and up-regulating the mRNA levels of apoptotic protease activating factor-1 (Apaf-1), Caspase-3, -8 and -9 and Fas ligand (FasL) in the gill of grass carp. Based on the quadratic regression analysis for the gill rot morbidity, C3 and MDA contents, the dietary lipids requirements for young grass carp have been estimated to be 5.60%, 6.01% and 4.58% diets., (Copyright © 2018. Published by Elsevier Ltd.)

The recent discovery of illicit drugs in the aquatic environment has raised concerns about the possible effects on the aquatic fauna, because of the pharmacological activity of these substances. Cocaine is an illicit drug widespread in surface waters since it is the third most widely used drug in North America, Western and Central Europe, and the second in Latin America and the Caribbean. The aim of this study was to evaluate the influence of environmental concentrations of cocaine on the gills of the European eel (Anguilla anguilla). The gills of male silver eels exposed to 20 ng L -1 of cocaine for fifty days were compared to control, vehicle control and post-exposure recovery ten days groups. The following parameters were evaluated: the thickness of the interlamellar epithelium (TIE), the length of the secondary lamellae (LSL) and the fraction of the interlamellar epithelium and the secondary lamellae occupied by the mucous cells (MC(IE-SL)FA) 3) the plasma cortisol and prolactin levels. After cocaine exposure, the gill epithelium appeared hyperplastic. The following changes were observed: proliferation in the interlamellar epithelium; partial and total fusion of the secondary lamellae, that appeared shortened and dilated; epithelial lifting and aneurism in the secondary lamellae. Moreover, in cocaine exposed eels, an increase in TIE and MC(IE-SL)FA and a decrease in LSL were observed. These changes were still present ten days after the interruption of cocaine exposure. Plasma levels of both cortisol and prolactin increased after cocaine exposure; ten days after the interruption of cocaine exposure, the plasma cortisol levels were still higher, whereas the plasma prolactin levels were lower, than control values. Our results show that even a chronic exposure to low environmental cocaine concentrations severely harms the eel gills, suggesting damages to their functions, and potentially affecting the survival of this species., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Gill histopathology is a valuable tool to evaluate ecosystems health, because the gill is a key site of waterborne pollutant uptake and the first target organ to their toxicity. Consequently, this makes it important in biomonitoring programs. This study aims to evaluate gill histopathological differences in Douro basin native fish species and determine possible associations with water quality and the ecological status classifications. Two native fish species (Pseudochondrostoma duriense and Luciobarbus bocagei) were sampled in four points of the Douro basin: two reference points, Ameixiosa (Paiva River) and Covelas (Bestança River), both classified with an excellent ecological status; and two disturbed points, Castro Daire (Paiva River) and Alvações do Corgo (Corgo River), categorized with a good and a moderate ecological status, respectively. Gill histopathological differences were qualitative and quantitatively analyzed. The histological analysis showed that, in all sampling locations, both species presented some degree of gill differences, such as epithelial lifting, lamellar fusion, and/or necrosis. The histopathological differences evaluation emphasized some variances in the responses between the two species. In nase, the filament and lamellar epithelium proliferation were the histopathological differences that better reflected the river ecological status classification, proving their usefulness in biomonitoring programs.

Black spot gill syndrome in the northern shrimp, Pandalus borealis, is caused by an apostome ciliate, Synophrya sp., found within the gill lamellae. Whole mount staining, thin section histology, electron microscopy, and molecular studies were carried out on infected gills. The Synophrya 18S rRNA from Pandalus borealis (Genbank accession no. KX906568) and from two portunid crab species, Achelous spinimanus (Genbank accession no. MH395150) and Achelous gibbesii (Genbank accession no. MH395151) was sequenced. Phylogenetic analyses confirmed the identity of these ciliates as apostomes. The 18S rRNA sequence recovered from P. borealis shared 95% nucleotide similarity with the sequences recovered from the portunid crab species suggesting that it is a different species of Synophrya. The invasive hypertrophont stages, with a distinctive macronuclear reticulum, ranged in size from 300 to 400 µm with as many as 5 large forms/mm 2 of gill tissue. Histotrophic hypertrophont stages and hypertomont stages were observed in these studies. The presence of the parasite was linked to the formation of melanized nodules (up to 9 nodules/mm 2 of gill tissue) by the host and in some cases to extensive necrosis. Other studies have reported Synophrya sp. infections in P. borealis from Greenland, Labrador and Newfoundland, but further studies are necessary to determine the prevalence of this parasite in the dense schools of northern shrimp in the North Atlantic. Questions remain as to the possibility of epizootics of this pathogen and its impact on northern shrimp populations., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Ammonia nitrogen exposure has been found to significantly increase the early apoptosis rates of gill cells, affect the contents of ATP and disturb expressions of calcium-related genes in clam Ruditapes philippinarum. Mitochondria are the centers for energy production, initiation of apoptosis and calcium signal regulation. It is hypothesized that gill mitochondrion is a target organelle for the ammonia nitrogen. Thus, ATP metabolism together with ATP-consuming functions would be interfered by ammonia exposure. In the present study, mitochondrial transmembrane potential (MTP), ATPase activities, gill functions in clearance and respiration, and histological changes were detected to characterize the effects of ammonia to the gill mitochondria in clam R. philippinarum. Results indicated that ammonia exposure led to significant decreases in MTP, Ca 2+ -ATPase activity and clearance rates. However, different concentrations of ammonia nitrogen induced different variations on H + , K + -ATPase activity and respiration rates. Histological observation revealed that subacute exposure of ammonia damaged the microstructure of gill tissues. Therefore, ammonia exposure dramatically damaged the normal structure and function of mitochondria, resulting in irreversible damage in energy formation and supply. In addition, it affected Ca 2+ and K + metabolism and inhibited food intake and respiration in clam R. philippinarum., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Industry demand for nanomaterials is growing, but metal nanoparticle toxicity is not fully understood. For example, nickel nanoparticles (NiNPs) are used in electric capacitors, and their consumption is increasing, but there have been few reports of their toxicity and environmental effects. To elucidate the toxicological characteristics of NiNPs, we investigated their effects on the histopathology and oxidative states of zebrafish (Danio rerio) and compared the results with those of ionic nickel. Zebrafish exposed to four different concentrations of NiNPs or NiCl 2 for 72 hr or 7 days were subjected to histopathological analysis, and tissue samples were subjected to analyses for oxidative stress and gene expression. High concentrations of both NiNPs and NiCl 2 caused tissue damage in the gills, digestive tract, and liver. The damage was typically characterized by epithelial degeneration and necrosis in the gills, esophagus, and intestines, as well as by lipid loss and palisade pattern degradation in the liver. The damages to the gills, esophagus, and intestines were more severe after exposure to NiNPs, but exposure to NiCl 2 led to more severe liver damage. Exposure to NiNPs increased lipid peroxidation in the skin but decreased it in the liver and intestines; exposure to NiCl 2 increased lipid peroxidation in the intestines. Only exposure to NiCl 2 changed antioxidative responses, enzymatic antioxidant activities, and metallothionein gene expression. These results indicate that NiNPs, which are highly adsorptive, cause severe damage to the epithelium by physical contact with the cell surface and production of reactive oxygen spices, whereas ionic nickel, which is absorptive, affects cellular antioxidative responses by absorption into the body and delivery to the liver.

Sugarcane vinasse is a residue generated at a rate fifteen times greater than the ethanol production. Because of its high organic and micronutrient content, this residue is used as a fertilizer on sugarcane crops. However, when used in large quantities, vinasse can saturate the soil and contaminate nearby water resources by percolation and leaching. Given the proven toxic potential of in natura vinasse, the present study aimed to evaluate the toxic potential of leached sugarcane vinasse using Nile tilapia (Oreochromis niloticus) as a test organism. A bioassay was performed after vinasse percolation in laboratory soil columns. The bioassay included one control group containing fresh water and two treatment groups, the first exposed to a 2,5% dilution of leached of vinasse and the second to a 2,5% dilution of in natura vinasse. After exposure, histopathological analysis was performed in gills and livers, and the latter were labelled for HSP70 proteins. No significant changes were detected in the gills of the exposed fish. However, in the liver, both in natura and leached vinasse induced statistically significant histopathological changes. These changes include hydropic degeneration, cell boundary losses, pyknotic nuclei and cellular disorganization. HSP70 expression significant increase in liver of both treatment groups were observed, being higher for the in natura vinasse exposed group. Results suggested that both leached vinasse and in natura vinasse were toxic, its still able to provoke histological changes and induce the cytoprotective response in exposed fish liver, evidenced by a immunostaining of cellular stress proteins. Thus, in order to reduce its environmental impact, appropriated effluent disposal is essential., (Copyright © 2018. Published by Elsevier Inc.)

Harmful algal blooms (HAB) are responsible for massive mortalities of wild and aquacultured fish due to noticeable gill damage, but the precise fish-killing mechanisms remain poorly understood. A non-invasive microelectrode ion flux estimation (MIFE) technique was successfully applied to assess changes in membrane-transport processes in a model fish gill cell line exposed to harmful microplankton. Net Ca 2+ , H + , K + ion fluxes in the rainbow trout cell line RTgill-W1 were monitored before and after addition of lysed cells of this Paralytic Shellfish Toxins (PST) producer along with purified endocellular dinoflagellate PST. It was demonstrated that PST alone do not play a role in fish gill damage during A. catenella outbreaks as previously thought, but that other ichthyotoxic metabolites from lysed algal cells (i.e. lipid peroxidation products or other unknown metabolites) result in net K + efflux from fish gill cells and thereby gill cell death., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Epitheliocystis is a skin and gill disease in fish caused by pathogenic intracellular bacteria. The disease has been reported in at least 90 species of marine and freshwater fish in both the southern and northern hemispheres. It affects a number of commercially important aquaculture species, including salmon, kingfish and bream. In infected fish, cysts typically develop in the gill epithelia, promoting the fusion of gill lamellae. Infections can lead to respiratory distress and death, particularly in cultured and juvenile fish with cases rarely reported in wild fish. Modern molecular techniques are challenging the conventional wisdoms regarding the epidemiology of epitheliocystis, showing now that a number of distinct bacterial pathogens from completely different phyla can cause this disease. Here, we review the state of knowledge, including updates on aetiology, host range, diagnosis and treatments. Traditionally, bacteria from the phylum Chlamydiae were the only known pathogenic agents of epitheliocystis, but aetiology is now recognized as being more complex, including a range of Proteobacteria. Notwithstanding recent advances in identifying the pathogens, the reservoirs and modes of transmission remain largely unknown. Recent genome sequencing of the growing number of epitheliocystis agents suggests that many bacteria causing this disease are unique to individual species of fish. Environmental conditions that approach or exceed animals' physiological tolerances (e.g. atypical temperature, salinity or pH levels) are thought to contribute to disease development and progression. Empirical data and evidence concerning epidemiology, aetiology and treatments are, however, in many cases limited, highlighting the need for more work to better characterize this disease across the different hosts and locales affected., (© 2018 Blackwell Verlag GmbH.)

Hemorrhagic septicemia of mandarin fish (Siniperca chuatsi) was mainly caused by Aeromonas hydrophila which was an opportunistic pathogen. In recent years, the disease has caused tremendous economic loss with high morbidity and mass mortality in the mandarin fish breeding industry. Histopathological analysis and the immune related gene expression profiles of mandarin fish (S. chuatsi) infected with A. hydrophila were investigated in this study. Transmission electron microscopy (TEM) images showed that the cells of A. hydrophila densely covered with a mass of fimbriae. Histopathological analysis revealed that inflammation, vacuolization and extensive necrosis existed in the gill, liver, spleen and head kidney of the diseased fish. Quantitative real-time PCR was performed to measure mRNA expression levels for six immune related genes in mandarin fish after A. hydrophila infection. The transcriptional analysis of these immune related genes demonstrated that the expression levels of major histocompatibility complex class II (MHC II), T cell receptor α (TCRα), tumor necrosis factor α (TNFα), CC chemokine 3, interleukin 8 (IL-8) and Hepcidin were strongly up-regulated in spleen and head kidney of mandarin fish post-infection. These results will contribute to further study on the pathogenesis and host defensive system in A. hydrophila infection., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Nanoparticles (NPs) enter the environment mainly through waste water effluents, accidental spillage, and industrial runoffs. This is worrying because NPs can enter the human body owing to their large aspect-to-size ratio and reactive surfaces that facilitate their penetration through biological barriers and thus can induce oxidative stress in host cells. Therefore, there is a growing concern about the toxicity of NPs, which needs to be addressed. Thus, this study investigated the ameliorative effects of Moringa oleifera seed extract (MOSE) in Cyprinus carpio exposed to copper nanoparticles (Cu-NPs). For the in vivo assessment of the shielding effects of MOSE, 240 samples of C. carpio (40-45 g) were randomly allocated to 24 experimental tanks (10 fish/tank of 40 L) 24 h prior to the start of this experiment. The experimental fish were faced with the water-born exposure of a pre-determined dose of 1.5 mg Cu-NPs/l along with pre- and post-treatment with different doses (100 or 200 or 300 mg l -1 ) of MOSE for 28 days. The MOSE showed significant ameliorative effect on the antioxidant defense, in response to the elevated levels of Cu-NP-induced oxidative stress. It also played a protective role as indicated by the suppression of the histological alterations in the gills and liver of fish exposed to the Cu-NPs. It was concluded that the Cu-NP-induced toxicity in C. carpio was ameliorated by the use of MOSE in this study. Moreover, the post-Cu-NP treatment stage showed more protective effects of MOSE than the pre-Cu-NP treatment phase. Further studies are suggested to determine the optimum dose and delivery method of MOSE for similar or different NP exposed fish.

Koi sleepy disease (KSD) is a disease with increasing importance in global common carp aquaculture. Despite the fact that carp edema virus (CEV) is most likely the causative agent of KSD, the disease often presents itself as multifactorial with several parasites and bacteria species present on gills, skin or in internal organs. Therefore, in this study, we analysed and presented initial results on an interaction of flavobacteria and CEV in the development of clinical KSD in carp suffering from proliferative gill disease. We examined selected field samples from Germany and Hungary and confirmed the presence of CEV and flavobacteria co-infections in subset of the samples. In several infection experiments, we studied the transfer and dynamics of both infections. Furthermore, we analysed which Flavobacterium species could be isolated from KSD-affected fish and concluded that Flavobacterium branchiophilum is a possible copathogen. Antibiotic treatment experiments showed that CEV seems to be the primary pathogen causing an insult to the gills of carp and by these enabling other pathogens, including F. branchiophilum, to establish co-infections. Despite the fact that F. branchiophilum co-infection is not required for the development of clinical KSD, it could contribute to the pathological changes recorded during the outbreaks., (© 2018 John Wiley & Sons Ltd.)

Many studies have investigated the potential negative effects of silver on aquatic organisms, but most focused on short-term exposure in few species. Moreover, there are many uncertainties about differences in potential toxicity mechanisms and adverse effects of silver nanoparticles (AgNPs) and ionic form of silver (AgNO 3 ). We investigated chronic effects of AgNPs and AgNO 3 on the juvenile common carp (Cyprinus carpio). AgNPs and AgNO 3 accumulated in the liver, gill and intestine, respectively and highest was related to AgNPs. Our results indicated, silver uptake was accompanied with histological alteration in the target organs such that different tissue lesions were observed in exposed groups. Superoxide dismutase (SOD), catalase (CAT) and lactate dehydrogenase (LDH) activity and also hsp70, ghrelin and IGF-1 genes expression were induced in both forms. After 7 days, highest hsp70 gene expression was observed in AgNO 3 treatment and highest ghrelin and IGF-1 gene expression was observed in AgNPs treatment. The results revealed that adverse effects of AgNPs on different aspects of the health of juvenile common carp, may not be solely a result of particle dissolution. In addition, the main toxic mechanism of AgNPs was probably related to the accumulation of silver followed by the molecular and oxidative stress response., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Aeromonas hydrophila is considered as a potential risk to fish populations in the aquaculture industry and could also pose a serious threat to humans. In this study, the impact of A. hydrophila infection in the air-breathing catfish, Clarias gariepinus was analyzed using a multidimensional approach. Aeromonas hydrophila (1 × 10 7 cells) was injected into C. gariepinus intraperitoneally and maintained at an ambient temperature and photoperiod with periodical monitoring for morphological changes. After 7 days post-infection, tissue samples of the gills, liver, intestine, and kidney were subjected to biochemical, histological, transmission electron microscope (TEM) and proteomic analyses. Observed results indicated distinct morphological changes with the significant increase of ROS and oxidative stress enzymes (CAT and SOD) in tissues of the infected group when compared to the control. Histological analysis in infected fish revealed the presence of pyknotic nuclei, early stages of necrosis in the liver, degradation of renal tubules and widened sinusoidal space in kidneys along with enlargement of the epithelial region in the intestine. TEM analysis of the infected intestine showed degeneration of villi and the presence of multinucleated erythrocytes. Two-dimensional proteomic and mass spectrometry analysis of intestine and liver displayed up-regulation of several immune regulatory proteins such as proteasome subunit 3 protein, prolactin and intermediated filament protein; and down-regulation of proteins including actin, serine/arginine-rich splicing factor and carbonic anhydrase. Taken together, these results suggest that the identified proteins may have a role in immune regulation against A. hydrophila infection in C. gariepinus and support further investigations of host-pathogen interactions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

DNA breakage has been frequently used as a biomarker of the pesticide toxicity. The present study introduced a method to quantify the DNA breakage in Oncorhynchus mykiss exposed to the pesticide malathion. Specimens were exposed to different concentrations of malathion for 1-9 days and their gill and liver were sampled. DNA was extracted and electrophoresed using agarose gel. The pixel density curves were obtained from the gel smears. The area under the curves was arbitrarily divided from three up to seven segments using a Java macro in the software ImageJ. Some weighted averaging methods were used to calculate DNA breakage in each gel lane. Akaike information criterion (AIC) was used to find the best analysis of variance. The liver was more sensitive than the gill showing a larger number of significant differences among the specimens exposed to various concentrations of malathion. The geometric weighted averaging on the data extracted from the seven-segment pixel density curve resulted to the lowest AIC. The double-strand DNA breakage of O. mykiss was able to detect malathion in freshwater in concentrations over 0.05 mg L -1 .

Humidifier disinfectants containing polyhexamethylene guanidine phosphate (PHMG-P) can induce pulmonary toxicity and has caused human casualties in South Korea since 2006. Thereby, the safety evaluation of household chemicals such as PHMG-P has garnered increased importance. However, many limitations, such as the lack of specialized facilities and animal welfare concerns associated with the use of murine models, persist. Zebrafish gills have high functional and structural similarity to mammalian lungs. Moreover, zebrafish are sensitive to toxic substances, resulting in changes in behavioral or ventilatory patterns. Based on these facts, in this study, we aimed to evaluate the pulmonary toxicity of PHMG-P in zebrafish. Zebrafish exposed to PHMG-P showed an increase in mRNA levels of inflammatory factors persisting for 28 days along with histopathologic changes in the gills. An exposure time-dependent alteration in infiltration of inflammatory cells and destruction of gill lamellae was observed. In addition, an increase in mRNA levels of fibrosis factors was observed in gills exposed to PHMG-P for 28 days, as assessed by collagen staining with Masson's trichrome. These results supported the cellular level results. Taken together, our results reveal pulmonary toxic effects of PHMG-P and suggest useful markers for evaluating pulmonary toxicity.

Sulfide is a harmful environmental pollutant that affects the survival and immunity of shrimps. The gill is important for shrimp respiratory and osmotic adjustment, the physiological and immune homeostasis of the organ can be influenced by sulfide. In this study, we investigated the acute toxicity of sulfide (5 mg/L) on the morphology, physiological and immune response in the gills of Litopenaeus vannamei. H&E stain showed that sulfide stress damaged the gills histological structure. Specifically, osmoregulation capacity including of Na + /K + -ATPase and Ca 2+ /Mg 2+ -ATPase activity was both increased at 6 h and 12 h, and decreased at 72 h; the contents of free amino acid including of Gly, Pro, Ser, Thr and Ala were decreased at 72 h. Respiratory metabolic enzymes, such as cytochrome c oxidase and succcinate dehydrogenase activity was decreased at 12 h-72 h, while fumarate reductase and lactate dehydrogenase activity kept a higher level at 12 h-72 h. Significant variations in the activities of immune enzymes (acid phosphatase, alkaline phosphatase, total antioxidant capacity and lysozyme). The expression of immune-related genes (heat shock protein 70, thioredoxin and caspase-3) was increased at first and then decreased, while hypoxia inducible factor 1α kept a higher level at 6 h-72 h. These results revealed that sulfide stress influenced the L. vannamei gills physiological and immune function by damaging histological structure, and confusing osmoregulation, respiratory metabolic and immune capacity., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The dusky grouper Epinephelus marginatus (Lowe) is an ecologically and commercially important fish species of the Atlantic and Mediterranean coastal rocky habitats. Despite records of didymozoid infections in several grouper species, the identification and pathogenesis of these parasites in E. marginatus are lacking. The aim of this study is to characterize the didymozoids of E. marginatus, particularly their mechanisms of infection and histopathological features. Dusky groupers (n = 205) were caught off Majorca Island (western Mediterranean Sea) and examined for parasites. Of the fish sampled, 45% were infected with white and yellow didymozoid capsules and brown nodules, found on the gills and pseudobranchs. Parasite abundance had a strong positive relationship with the fish length; only fish larger than 20 cm were infected, suggesting infection via consumption of an intermediate host, for which E. marginatus size was a limiting factor. The capsules contained two convoluted viable adult trematodes, identified as Didymodiclinus sp., in close contact with host capillary vessels, with no evidence of the tissue inflammatory response. Conversely, nodules containing degraded parasites were surrounded by an intense inflammatory infiltrate. The findings suggest that Didymodiclinus sp. have the potential to evade the host's immune system by inhibiting the inflammatory response., (© 2018 John Wiley & Sons Ltd.)

Freshwater bathing is one of the main treatment options available against amoebic gill disease (AGD) affecting multiple fish hosts in mariculture systems. Prevailing freshwater treatments are designed to be long enough to kill Neoparamoeba perurans, the ectoparasite causing AGD, which may select for freshwater tolerance. Here, we tested whether using shorter, sublethal freshwater treatment durations are a viable alternative to lethal ones for N. perurans (2-4 hr). Under in vitro conditions, gill-isolated N. perurans attached to plastic substrate in sea water lifted off after ≥2 min in freshwater, but survival was not impacted until 60 min. In an in vivo experiment, AGD-affected Atlantic salmon Salmo salar subjected daily to 30 min (sublethal to N. perurans) and 120 min (lethal to N. perurans) freshwater treatments for 6 days consistently reduced N. perurans cell numbers on gills (based on qPCR analysis) compared to daily 3 min freshwater or seawater treatments for 6 days. Our results suggest that targeting cell detachment rather than cell death with repeated freshwater treatments of shorter duration than typical baths could be used in AGD management. However, the consequences of modifying the intensity of freshwater treatment regimes on freshwater tolerance evolution in N. perurans populations require careful consideration., (© 2018 John Wiley & Sons Ltd.)

The Gulf of Mexico, including the southwest Florida coast, USA, experience recurrent blooms of the brevetoxin (PbTx)-producing dinoflagellate, Karenia brevis. Northern quahogs (hard clams) Mercenaria mercenaria, are an important commercial species in this region. This study examined the effects of field and laboratory exposure of adult clams to K. brevis during their reproductive period, and effects on their subsequently produced offspring. Ripe adult clams were collected from a site which had been exposed to an eight-month natural bloom of K. brevis and an unaffected reference site. Ripe adult clams were also exposed to bloom concentrations of K. brevis for 10 days in the laboratory. Clams exposed to K. brevis accumulated PbTx at concentrations of 1508 (field exposure), 1444 (1000 cells mL -1 laboratory treatment) and 5229 ng g -1 PbTx-3 eq (5000 cells mL -1 laboratory treatment). Field-exposed clams showed histopathological effects: a significantly higher prevalence of mucus in the stomach/ intestine (23.3%), edema in gill tissues (30%) and presence of the cestode parasite, Tylocephalum spp. in whole tissue (40%), compared to non-exposed clams (0, 3.3 and 6.7% respectively). These clams also showed reduced gonadal allocation (23% gonadal area) and a higher prevalence of clams of undetermined sex (20%) compared to those sampled from the non-exposed site (43% and 0%, respectively). It is hypothesized that less energy may be channeled into reproduction as more is allocated for homeostasis or tissue repair. The fertilization success of gametes obtained from both field and laboratory-exposed adults was significantly lower in clams that had been exposed to K. brevis and development of these offspring was negatively affected at Days 1 and 4 post-fertilization (in field- and laboratory-exposed clams at the higher K. brevis concentration and in laboratory-exposed clams at the higher K. brevis concentration, respectively). Negative effects may be due to toxin accumulation in the gametes of field-exposed clams (244 ± 50 ng PbTx g -1 and 470 ± 82 ng g -1 wet weight in oocytes and sperm, respectively). Adverse effects in M. mercenaria are compared to those previously reported in oysters, Crassostrea virginica, under similar conditions of exposure. This study provides further evidence of the impacts of K. brevis and its associated toxins on the adults and offspring of exposed shellfish. Site-selection for the collection of broodstock and aquaculture grow-out efforts should therefore consider the local occurrence of K. brevis blooms., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Atrazine is a herbicide that is banned in Europe but remains widely used on different types of crops in several countries in the American continent. Atrazine is known to be an endocrine disruptor and its effects on gonads have been extensively reported, but the toxic action on other organs is poorly documented. In this paper, we investigated the toxicity of atrazine on the gills and spleens of Nile tilapia (Oreochromis niloticus). The median lethal concentration (LC 50 ), capable of killing one-half of the test animals was calculated, and sublethal concentrations of atrazine were used in a semistatic and subchronic assay. The following four experimental groups were formed: control not exposed to atrazine, a group exposed to 1 ppm atrazine for 15 days, a group exposed to 2 ppm for 7 days, and a group exposed to 2 ppm for 15 days. The concentrations were verified during the study by high performance liquid chromatography. The gills and spleens were stained with hematoxylin and eosin and histopathological findings were made. The Perls technique was used on the spleens to identify hemosiderin, lipofuscin, and melanin pigments in the cells from melanomacrophage centres (MMCs). The spleens were submitted to proliferating cell nuclear antigen (PCNA) and inducible nitric oxide synthase (iNOS) immunohistochemistry, and morphometry was used to assess splenocyte proliferation and melanomacrophage iNOS expression. Finally, a colorimetric assay for caspase-3 was performed on the spleens to identify apoptosis. Vascular and structural alterations, such as venous sinus congestion, aneurysm, hemorrhage, pillar cell hypertrophy, disarrangement of secondary lamellae, and epithelial lifting were observed in the gills. The frequency of individuals with aneurysms was higher in the groups treated with 2 ppm than in other groups. Atrazine had an immunomodulatory effect on the spleen, observed by the alteration in the percentage of red and white pulp, alteration of the MMC area, changes in the melanomacrophage pigment content, slight iNOS suppression, decrease in splenocyte proliferation under 1 ppm atrazine, and increased caspase 3 activity under 2 ppm atrazine after 7 and 15 d. Such effects could compromise oxygenation and the immune response and, ultimately, the survival and fitness of the fish., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Gill disorders have become a significant problem during the marine phase of farming Atlantic salmon (Salmo salar L.). The term complex gill disease (CGD) includes a wide range of clinical gill disease presentations generally occurring from the end of summer to early winter on marine Atlantic salmon farms. The gross and histological lesions observed are the resultant culmination of exposure to a mixture of environmental insults, pathogenic organisms and farm management practices. None of the three principal agents purportedly associated with CGD (Desmozoon lepeophtherii, salmon gill poxvirus or Candidatus Branchiomonas cysticola) have been cultured successfully in-vitro, so individual in-vivo challenge studies to identify their pathogenesis have not been possible. Studies of cohabitation of single pathogen-infected fish with naïve fish, and epidemiological investigations are required urgently to elucidate the roles of these pathogens and other factors in CGD., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Recently, momentous consideration has being given to our natural ecosystems due to toxic metals, insidious to our environment execute as pollutants to the freshwater ecosystems. The accumulations of metals were encompassed with lead, cadmium and chromium in organs of Devario aequipinnatus. Although, the microscopic scrutinization from the gill and liver of the fish species were explored, the crucial conditions of the ecosystem. The histological study plays a key role in determining the effects of pollution. In the length-weight relationships of the regression parameters of coefficient value r 2 , 'a' value and 'b' value were showed the negative allometric growth rate of species D. aequipinnatus. However, the nucleotide sequence blast search was performed in NCBI database. In that the species of D.aequipinnatus were closely associated with other sub-species but within same genus, and it showed the similarity range between 100% and 90% in reference to other species for phylogenetic analysis.

This study investigated the action of titanium dioxide nanoparticles (TiO 2 -NPs), on the gills and kidneys of Neotropical freshwater fish, Prochilodus lineatus, with emphasis on reactive oxygen species (ROS) production, antioxidant responses, and morphological changes. Fish were exposed to 1, 5, 10, and 50 mg L -1 nominal TiO 2 -NPs suspended into water for 2 or 14 days. In gills, ROS decreased and glutathione (GSH) increased after 2 days, while ROS and GSH increased and superoxide dismutase activity decreased after 14 days. In kidneys, GSH and lipoperoxidation increased after 2 days and catalase activity decreased after 14 days. Common histopathologies in gills were epithelium hyperplasia, cellular hypertrophy, proliferation of mitochondria-rich cells (MRC), and lamellar stasis; in kidneys, there were cellular and nuclear hypertrophy, focal tubule degeneration, necrosis, and melanomacrophage (MM) proliferation. Although environmentally unlikely, high-dose exposures clarified biological effects of TiO 2 -NPs, such as ROS formation and MRC responses in the gills, which may impair ionic balance. It was also found that MM are likely responsible for eliminating NPs in the kidney. These findings will help to regulate TiO 2 -NP disposal, but longer-term studies are still needed.

Water mites of the genus Unionicola are the most common symbionts of freshwater bivalves. During the current investigation, a total of 120 live freshwater mussels representing 5 species, Corbicula fluminea (Veneroida), Coelatura aegyptiaca (Unionoidea), Mutela rostrata, and Chambardia rubens (Mutelidae), were collected from 2 localities in Tura (Helwan Governorate) and El Kanater (Qaluobiya Governorate), Egypt. Only 3 of the 4 bivalve species listed are considered freshwater bivalves (members of Unionoidea). Corbicula fluminea belong to the family Cyrenidae within Veneroida. Collected mussels were dissected and examined for the presence of unionicolid mites. It was found that 30.83% (37/120) were infected with a single mite species, Unionicola tetrafurcatus (Unionicolidae). The highest prevalence was observed during the summer with 83.33% (25/30) whereas the least was observed in autumn, i.e., 33.33% (10/30). Mites were recovered from the gills, gonads, and visceral mass of mussel hosts. Gills of host mussels were the primary site of oviposition for Unionicola mites. Smaller bivalves in size had significantly greater numbers of mites than did larger ones in size. Numbers of mites per host species was variable and the highest prevalence level of 83.33% (25/30) was recorded in Cor. fluminea while the lowest one of 16.66% (5/30) was found in Ch. rubens. Morphological and morphometric characterizations of mites revealed some differences between the present species and other related Unionicola. Histopathological responses of host mussels to the eggs, larvae, and cuticular remnants of U. tetrafurcatus were also studied. Therefore, the present study demonstrated that freshwater bivalves have a new host and locality records for infection with U. tetrafurcatus. Future studies are recommended to include advanced molecular characteristics for these mites.

The present study describes, for the first time, histopathological alterations in the gills of Macrobrachium amazonicum caused by infestation of Probopyrus bithynis (Isopoda: Bopyridae). In every case (100%), the infestation by P. bithynis was by a single pair of parasites (male and female) and occurred in the right or left side of the branchial chamber; the gill structures were visibly compressed due to the presence of parasites. The gills of M. amazonicum parasitized by P. bithynis exhibited a chronic inflammatory response, with the presence of edema, greater quantities of hemocytes, necrosis, epithelial cell hyperplasia, rupture of the pillar cells at the ends of the gill lamellae, desquamation of the cuticle, lamellar fusion and rupture of the lamellar epithelium. Tissue lesions were found in the histological sections of the gills of the parasitized M. amazonicum. Structural alterations in the branchial chamber of the hosts caused by the presence of P. bithynis can lead to physiological changes that can impair host respiratory performance. Finally, histopathological alterations in the branchial chamber of hosts suggest that P. bithynis feed directly on the gill tissues of this shrimp.

Different types of metal oxide nanoparticles (NPs) have been suggested for various applications such as water treatment and construction of agricultural pesticides; however, there are concerns about the potential toxicity of these compounds for the nontarget organism especially aquatic organisms. The aims of this study were assessing toxicity and histopathological effects of copper oxide NPs (NPs-CuO) on common carp (Cyprinus carpio) as a model organism. For this purpose 150 common carp with an average weight 7 ± 1 g were exposed to 0, 10, 20, 30, 40, 60, 80, 100, 150, and 200 mg/l of CuO-NPs (10 treatment with three replicates) for 96 hrs. After 24, 48, 72, and 96 hrs exposures, mortality rates recorded and gill samples were collected. Statistical analysis showed significant differences in carp survival between control and treatment groups (p < 0.05); regression between fish mortality rate and NPs-CuO concentration was also revealed (p < 0.01). The LC 50 96h of NPs-CuO for common carp was estimated as 124.9 mg/l in this study. Various tissue damages were observed in gill of treatments; such as, hypertrophy, hyperplasia, lamellar fusions, erythrocyte infiltration, epithelial lifting; also, there was significant correlation between intensity of tissue lesions and concentration of NPs-CuO (p < 0.01). The findings of the present study demonstrate that sublethal concentration of NPs-CuO can lead to serious tissue lesions. Whats more, concentrations above 30 ml/l of NPs-CuO can lead to some clinical signs; such as skin darkening and death with open mouth as well as definite fish death., (© 2018 Wiley Periodicals, Inc.)

Gill diseases cause serious losses in farming of Atlantic salmon and the number of agents involved increases. Salmon gill poxvirus (SGPV) and the gill disease in causes where SGPV apparently was the only disease-causing agent were initially characterized. Recently, it was further shown that SGPV can be a common denominator in widely different multifactorial gill diseases. Here, we present the challenge of diagnosing gill disease with SGPV in salmon fry of 0,3-5 grams. Apoptosis of gill lamellar epithelial cells and hemophagocytosis was also observed in fry similar to findings in smolts and grow-out fish. Using our newly developed immunohistochemistry method, we further demonstrate that some of the apoptotic epithelial cells covering the oral cavity were positive for SGPV. Thus, SGPV is not restricted to respiratory epithelium alone and may infect the fish at very early life stages. Furthermore, as the cases examined here are from Norway, Faroe Island and Scotland, we show that SGPV is more widespread than previously reported., (© 2018 John Wiley & Sons Ltd.)

A Myxobolus species and a Thelohanellus species infecting Carassius auratus gibelio (Bloch, 1782) were redescribed by their morphological, histological and molecular characterization. In the present study, the Myxobolus species infecting the muscle was identified as Myxobolus kingchowensis Chen et Ma, 1998 by the morphological and molecular data. Histologically, mature spores of M. kingchowensis were observed in the intercellular and connective tissue of muscle, though the plasmodia were not found. In addition, scattered spores also occurred in the intercellular of haematopoietic cells, intraepithelial of the renal tubules and interior of the melano-macrophage centres. Phylogenetic analysis showed that M. kingchowensis clustered in the clade of muscle-infecting Myxobolus species, further supporting muscle as the infection site of M. kingchowensis. The present Thelohanellus species infecting the gills was identified conspecific as Thelohanellus sinensis reported in Sun (2006) (mark it as T. sinensis-Sun)based on spore morphology, biological traits (host specificity and organ specificity), and molecular data. However, compared with the original description of T. sinensis Chen et Hsieh, 1960, the present Thelohanellus species and T. sinensis-Sun both infecting the gills of gibel carp are distinguishable from the original description in the host and infection site, which made the validity of T. sinensis-Sun dubious. Due to the absence of molecular data in the original description of T. sinensis, we suggest marking the present species and T. sinensis-Sun as T. cf. sinensis to avoid the confusion until T. sinensis is obtained from the type host and type infection site.

Location and tissue preference of filamental-type myxosporean plasmodia in histological slides of the gills can be properly identified only in cross sections of the gill filaments. The authors selected three myxosporeans (Myxobolus rutili, M. dispar and Henneguya psorospermica, parasites of the roach, the common carp and the pike, respectively) for studying the problem. The plasmodia of these species studied in longitudinal sections were earlier regarded as developing inside the filamental arteries. Cross sections of the filaments showed that all the three species developed plasmodia in the dense connective tissue constituting the adventitia of gill arteries and covering the cartilaginous gill rays. Myxobolus rutili started its development close to the afferent branchial artery but attached to the cartilaginous gill ray. More developed plasmodia of this species surrounded the rays. Plasmodia of M. dispar were formed on the inner side of the afferent branchial artery, while those of H. psorospermica were located at the external side of the efferent branchial artery.

Pedunsaponin A, a novel molluscicidal compound isolated from Pueraria peduncularis, exhibits strong toxicity against Pomacea canaliculata. To determine the mechanisms of Pedunsaponin A toxicity, its effects on the organs and hemocytes of P. canaliculata were examined in this study. The results showed that Pedunsaponin A had significant toxic effects on different organs of the snail, including the lungs, gills, mantle, siphon tube, ventricle, pericardial cavity, hepatopancreas, kidneys, and the major symptom of this toxicity was the loss of cilia in the lungs and gills. Additionally, in further studies on the effects of Pedunsaponin A treatment, we found that the hemocyte count was changed and hemocyte morphology was damaged, which was primarily reflected by cytoplasm leakage, nuclei deformation, and significant reductions in the number of ribosomes and granulocyte mitochondria. Based on these results and considering that blood vessels are distributed in the lungs and gills, we hypothesized that Pedunsaponin A would first destroy the cilia, which disrupt physiological activities such as respiration, excretion and feeding, and then enter the hemolymph through blood vessels, disrupt the normal function of the hemocytes and destroy the snail immune system, eventually resulting in the death of the snail., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The aim of the present work was to isolate probiotic bacteria from the intestinal tract of healthy freshwater prawn Macrobrachium rosenbergii and to examine the effect of the isolated probiotic Bacillus vireti 01 in controlling Pseudomonas aeruginosa infection. This is probably the first report on the isolation of probiotic B. vireti 01 from the intestine of M. rosenbergii. The compounds present in B. vireti 01 were identified using GC-MS analysis. The effect of B. vireti 01-incorporated diet on survival and antioxidant enzymes was studied in M. rosenbergii for 2 weeks. Decreased mortality was observed in M. rosenbergii which were administered with the probiotic diet compared to control diet. The antioxidant defence enzymes activities such as SOD, catalase and GSH were analysed in various organs of M. rosenbergii probiotic-treated and control groups. Antioxidant enzyme activities were considerably lowered (p < 0.01) in the muscles, hepatopancreas and gills of prawns infected by P. aeruginosa when compared to that of prawns fed with the probiotic-supplemented diet. The histopathological results suggest that the hepatopancreas, gills and muscles infected with P. aeruginosa were altered structurally. The result of the present work demonstrates that the probiotic B. vireti 01 could be used as a substitute to antibiotics for treating P. aeruginosa infection in prawns.